If you start putting very large numbers of human brain cells into primates, suddenly you might transform primates into something that has some of the capacities that we regard as distinctively human – speech or other ways of being able to manipulate or relate to a human. These possibilities, at the moment, are largely being explored in fiction but we need to start thinking about them now."

Where people worry is when you get to the brain, the germ cells and the sentinel features that help people recognize what is a person, as opposed to a rat or a rabbit. Things like skin texture, facial shape, speech, replacing brain cells with human cells, allowing the development of human germ cells in animals. And particularly where there is any possibility of fertilisation within an animal.

Changing animals by putting human genes or cells into their structure is one way of making them more resemble the bit of the human condition you're interested in studying.

Do we trivialize a sublime feeling if we appreciate its dependence on the brain? Not in the least. Its significance does not depend on its being a soul state or a brain state...Humility bids us to take ourselves as we are; we do not have to be cosmically significant to be genuinely significant.

Paul Erdős, in a standard greeting he would make when he was not contemplating some mathematical problem, as quoted in My Brain Is Open : The Mathematical Journeys of Paul Erdos (1998) by Bruce Schechter, p. 10

I regard the brain as a computer which will stop working when its components fail. There is no heaven or afterlife for broken down computers; that is a fairy story for people afraid of the dark.

Although previously the monoamine systems were considered to be responsible for the development of major depressive disorder (MDD), the available evidence to date does not support a direct causal relationship with MDD. There is no simple direct correlation of serotonin or norepinephrine levels in the brain and mood. In other words, after a half-century of research, the chemical-imbalance hypothesis as promulgated by the drug companies that manufacture SSRIs and other antidepressants is not only without clear and consistent support, but has been disproved by experimental evidence.

A few decades ago, it was unthinkable that looking at the brain to understand representations of social groups such as black versus white was even possible, let alone that such explorations could yield useful knowledge.

On the floor of the midbrain is the ventral segmental system, that neurobiologists call region A10. Cells soaked in dopamine, certain emotions are processed here: such as the thoughts of two lovers - or a parent and a child.

People who had damage to the right cerebral hemisphere were unable to recognise simple patterns, or enjoy music, but they could still speak normally. People with left-brain damage were able to recognise patterns, but their speech was impaired. Obviously, then, the left deals with language, and you would expect a split-brain patient to be unable to read with his right eye (connected, remember, to the opposite side of the brain). Sperry's patient was also unable to write anything meaningful (i.e., complicated) with his left hand. They noticed another oddity. if the patient bumped into something with his left side, he did not notice. And the implications were very odd indeed. Not only did the split-brain operation give the patient two separate minds; it also seemed to restrict his identity, or ego, to the left side. When they placed an object in his left hand, and asked him what he was holding, he had no idea. Further experiments underlined the point. If a split-brain patient is shown two different symbols -- say a circle and a square -- with each eye, and is asked to say what he has just seen, he replies, 'A square'. Asked to draw with his left hand what he has seen, and he draws a circle. Asked what he has just drawn, he replies: 'A square'. And when one split-brain patient was shown a picture of a nude male with the right-brain, she blushed; asked why she was blushing, she replied truthfully: 'I don't know'. The implications are clearly staggering. The person you call 'you' lives in the left side of your brain. And a few centimeters away there is another person, a completely independent identity. Where language is concerned, this other person is almost an imbecile. In other respects, he is more competent than the inhabitant of the left-brain; for example, he can make a far more accurate perspective drawing of a house. In effect. the left-brain person is a scientist, the right-brain an artist.